What is the preferred initial screening test for acromegaly?

• A. Serum GH level.
• B. Serum IGF-1 level (followed by OGTT for GH suppression).
• C. MRI of the pituitary.
• D. DEXA scan.

Answer: (B)

The main idea is that screening for acromegaly looks for a hormone signal that reliably reflects long-term GH activity. Growth hormone itself fluctuates a lot during the day, so measuring a single GH value can be misleading. Instead, the body’s growth-promoting mediator, IGF-1, serves as a more stable and integrated indicator of GH action over time.

An elevated serum IGF-1 level is the best initial screening test because IGF-1 levels rise when GH is consistently high and, unlike GH, stay relatively constant. If IGF-1 is elevated, the next step is an oral glucose tolerance test to see if GH can be suppressed. In a person without acromegaly, GH falls to very low levels after a glucose load; in acromegaly, GH remains inadequately elevated despite the glucose challenge. This GH suppression test confirms the diagnosis.

Imaging with MRI of the pituitary is used afterward to locate a pituitary adenoma once elevated IGF-1 and lack of GH suppression have established biochemical acromegaly. DEXA scans assess bone density and are not used to screen for acromegaly.